An allergen is any foreign substance that triggers an allergic reaction. Your immune system views such substances as dangerous and triggers a defense mechanism. More than 50 million Americans of all walks of life, roughly one out of every five, suffer from various allergies, according to the Allergy and Asthma Foundation of America.

Types of Allergens

There are several types of allergens that affect human beings, with each coming into contact with your body in its own unique way. Some allergens can be introduced into your body through drinking or eating foods that contain the substance that you are sensitive to, inhalation, direct contact with the skin, or through injection via bee or wasp stings, and syringes (for drugs such as penicillin).

  • Animals-Proteins found in animal skin, urine, dander and saliva can trigger allergic reactions. Household pets such as dogs and cats are the most common sources of animal-linked allergens
  • Eggs and all egg-based products such as mayonnaise and marshmallows
  • Peanuts and tree nuts such as cashew nuts, walnuts and macadamia nuts
  • Shellfish such as crabs, abalone, shrimp, crayfish and prawns
  • Milk and milk products such as cheese and milk powder
  • Pollen and dust mites
  • Latex
  • Poison ivy- Collective term for three indigenous American plants that include poison ivy, poison sumac and poison oak
  • Wheat and all wheat-based products
  • Soy and all soy-based products
  • Insect stings- Common sources of insect stings include fire ants, wasps, bees, yellow jackets and hornets

Symptoms of Allergens

Sensitivity to an allergen varies from one individual to another, and it isn’t uncommon to find individuals who are allergic to a wide range of substances. The symptoms also vary depending on the type of the allergen and on the person’s sensitivity to the allergen.

In some instances, some individuals can suffer from anaphylaxis, a deadly form of allergic reaction which can result in immediate death if not promptly treated. The most common symptoms of reaction to allergens include:

  • Swelling and inflammation of body parts
  • Sneezing, wheezing and other respiratory problems
  • Itchy skin and hives
  • Dizziness
  • Swollen tongue and hoarse voice
  • Sudden drop in blood pressure
  • Itchy, red and watery eyes

Testing for Reaction to Allergens

Two broad types of tests-skin tests and blood test- can be done to determine whether a person is allergic to a certain allergen.

Skin Tests

This involves placing a suspected allergen on or under the skin to see whether a reaction will develop. One such test, called the skin prick test, involves placing a small solution containing the allergen on top of the skin and then scratching or pricking it with a needle to see whether an allergic reaction-usually a red, itchy and raised area called a wheal-develops. This confirms that the person is allergic to the substance.

Another skin test is the intradermal test which involves injecting a drop of a solution containing the allergen into the skin. This one is mostly used if a person is suspected to react to a certain allergen but the skin prick test is unable to validate this.

The skin patch test involves taping a pad containing an allergen solution on the skin for 24-72 hours. This test is used to diagnose a skin allergy known as contact dermatitis.

Blood Test

This test involves analyzing the presence of antibodies in the blood. The most common type of blood testing is ELISA, which measures the level of an antibody called immunoglobulin E that is usually generated by the body in response to some allergens. Other blood tests include radioallergosorbent testing (RAST and immunoassay capture test.

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